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nanotimes News in Brief
num but the corner columns are mixed. By supple- menting the high-resolution TEAM images with data from other experimental techniques it was possible to use brightness and contrast to calculate the kinds of atoms in each column.
By employing first-principles calculations, team members Colin Ophus and Mark Asta were able to model the effect of lithium on the solid-state preci- pitation of scandium, stimulating a sudden burst of nucleation, and also to understand why, because of the thermodynamic properties of the two metals interacting with aluminum and with each other, the precipitates are so uniform and stable.
Radmilović says, “Colin and Mark showed that lithi- um and scandium like each other. They also showed that by using the aluminum columns as a standard, we can calculate the intensity of the scandium and lithium by the brightness of the spot.” In the shells, the corner columns contain aluminum and about 10-percent lithium. In the cores, the corner columns contain all three metals.
U. Dahmen says: “In recent years there has been a rapid increase in the use of ‘integrative microscopy’ – using a variety of techniques such as high-angular annular dark-field imaging, high-resolution phase contrast, and energy-filtered imaging and spectrosco- py to attack a single problem. The TEAM microscope, which is corrected for both chromatic and spherical aberration, is unique in its ability to do all these techniques with high resolution. Understanding why nanoinclusions in aluminum-scandium-lithium are uniform is one of the best examples for the need to use integrative microscopy.”
11-08 :: August 2011
As good an alloy as aluminum-scandium-lithium is, its use may be limited by the cost of rare scandium, presently ten times the price of gold. By understan- ding how the alloy achieves its remarkable characte- ristics, the researchers fully expect that other systems with core-shell precipitates can be controlled by the same mechanisms, leading to new kinds of alloys with a range of desirable properties.
V. Radmilovic, C. Ophus, E. A. Marquis, M. D. Rossell, A. Tolley, A. Gautam, M. Asta, U. Dahmen: Highly monodis- perse core–shell particles created by solid-state reactions, In: Nature Materials, Vol. 10(2011), No. 9, September 2011, Pages 710-715, DOI:10.1038/nmat3077: http://dx.doi.org/10.1038/nmat3077